This invention relates to a demodulator for an amplitude modulated signal (hereinafter referred to an AM signal).
The conventional demodulator for an AM signal having a high input impedance comprises an emitter-follower transistor biased as a class B or C amplifier. An input AM signal is applied to the base of the transistor and an output is derived from the emitter thereof. Such demodulator, however, is a half-wave rectifier, and thus has a low demodulating gain. Further, in order to attain an adjustment-free intermediate frequency (IF) amplifier in a radio receiver, it has been suggested to replace IF transformers by ceramic filters. However, the ceramic filter has an extremely high output impedance, so that an input voltage applied to the demodulator decreases, resulting in a small demodulated output.